Move kernel version/capabilities detection to NewDaemon

Docker-DCO-1.1-Signed-off-by: Solomon Hykes <solomon@docker.com> (github: shykes)

daemon/daemon.go

@@ -8,6 +8,7 @@ import (
 	"os"
 	"path"
 	"regexp"
+	"runtime"
 	"strings"
 	"sync"
 	"time"
@@ -29,6 +30,7 @@ import (
 	"github.com/docker/docker/pkg/namesgenerator"
 	"github.com/docker/docker/pkg/networkfs/resolvconf"
 	"github.com/docker/docker/pkg/parsers"
+	"github.com/docker/docker/pkg/parsers/kernel"
 	"github.com/docker/docker/pkg/sysinfo"
 	"github.com/docker/docker/pkg/truncindex"
 	"github.com/docker/docker/runconfig"
@@ -767,6 +769,10 @@ func NewDaemonFromDirectory(config *daemonconfig.Config, eng *engine.Engine) (*D
 	if os.Geteuid() != 0 {
 		log.Fatalf("The Docker daemon needs to be run as root")
 	}
+	if err := checkKernelAndArch(); err != nil {
+		log.Fatal(err)
+	}
+
 	// set up the TempDir to use a canonical path
 	tmp := os.TempDir()
 	realTmp, err := utils.ReadSymlinkedDirectory(tmp)
@@ -1156,3 +1162,27 @@ func (daemon *Daemon) ImageGetCached(imgID string, config *runconfig.Config) (*i
 	}
 	return match, nil
 }
+
+func checkKernelAndArch() error {
+	// Check for unsupported architectures
+	if runtime.GOARCH != "amd64" {
+		return fmt.Errorf("The Docker runtime currently only supports amd64 (not %s). This will change in the future. Aborting.", runtime.GOARCH)
+	}
+	// Check for unsupported kernel versions
+	// FIXME: it would be cleaner to not test for specific versions, but rather
+	// test for specific functionalities.
+	// Unfortunately we can't test for the feature "does not cause a kernel panic"
+	// without actually causing a kernel panic, so we need this workaround until
+	// the circumstances of pre-3.8 crashes are clearer.
+	// For details see http://github.com/docker/docker/issues/407
+	if k, err := kernel.GetKernelVersion(); err != nil {
+		log.Printf("WARNING: %s\n", err)
+	} else {
+		if kernel.CompareKernelVersion(k, &kernel.KernelVersionInfo{Kernel: 3, Major: 8, Minor: 0}) < 0 {
+			if os.Getenv("DOCKER_NOWARN_KERNEL_VERSION") == "" {
+				log.Printf("WARNING: You are running linux kernel version %s, which might be unstable running docker. Please upgrade your kernel to 3.8.0.", k.String())
+			}
+		}
+	}
+	return nil
+}

docker/docker.go

@@ -9,7 +9,6 @@ import (
 	"net"
 	"os"
 	"path/filepath"
-	"runtime"
 	"strings"
 
 	"github.com/docker/docker/api"
@@ -19,7 +18,6 @@ import (
 	"github.com/docker/docker/engine"
 	"github.com/docker/docker/opts"
 	flag "github.com/docker/docker/pkg/mflag"
-	"github.com/docker/docker/pkg/parsers/kernel"
 	"github.com/docker/docker/sysinit"
 	"github.com/docker/docker/utils"
 )
@@ -118,12 +116,6 @@ func main() {
 			flag.Usage()
 			return
 		}
-
-
-		if err := checkKernelAndArch(); err != nil {
-			log.Fatal(err)
-		}
-
 		eng := engine.New()
 		// Load builtins
 		if err := builtins.Register(eng); err != nil {
@@ -255,27 +247,3 @@ func main() {
 func showVersion() {
 	fmt.Printf("Docker version %s, build %s\n", dockerversion.VERSION, dockerversion.GITCOMMIT)
 }
-
-func checkKernelAndArch() error {
-	// Check for unsupported architectures
-	if runtime.GOARCH != "amd64" {
-		return fmt.Errorf("The Docker runtime currently only supports amd64 (not %s). This will change in the future. Aborting.", runtime.GOARCH)
-	}
-	// Check for unsupported kernel versions
-	// FIXME: it would be cleaner to not test for specific versions, but rather
-	// test for specific functionalities.
-	// Unfortunately we can't test for the feature "does not cause a kernel panic"
-	// without actually causing a kernel panic, so we need this workaround until
-	// the circumstances of pre-3.8 crashes are clearer.
-	// For details see http://github.com/docker/docker/issues/407
-	if k, err := kernel.GetKernelVersion(); err != nil {
-		log.Printf("WARNING: %s\n", err)
-	} else {
-		if kernel.CompareKernelVersion(k, &kernel.KernelVersionInfo{Kernel: 3, Major: 8, Minor: 0}) < 0 {
-			if os.Getenv("DOCKER_NOWARN_KERNEL_VERSION") == "" {
-				log.Printf("WARNING: You are running linux kernel version %s, which might be unstable running docker. Please upgrade your kernel to 3.8.0.", k.String())
-			}
-		}
-	}
-	return nil
-}